"Singular sandstones"

The "singular sandstones" are rocks found at the northern end of the Les Fours, near the Rocher du Bonhomme. These sandstones were initially described by Horace Bénédicte de Saussure, an 18th-century geologist and one of the founders of mountaineering!
Why is this particular stone called this? Because it looked like nothing known at the time! These precious clues prove that only the inner part of the Mont-Blanc massif was formed during the Jurassic period.